Over at the Balkinization blog, I have a post with historical perspective on emerging debates among some Democrats over whether, if they have the political power to do so after 2020, they ought to increase the size of the Supreme Court. Here are some excerpts:

The circumstances favoring FDR’s Court-packing plan would seem to be about as favorable as might be imagined, yet FDR not only lost the Court-packing battle, that loss was politically devastating for the New Deal overall.  
          First, let’s recall just how breathtaking and profound the Court’s conflict was in that era with FDR’s and Congress’ policies.  The major highlights are widely known and still taught in law schools – the Court’s invalidation of the National Industrial Recovery Act (NIRA) or the Agricultural Adjustment Act (AAA).   
          But here is a sense of the range of national and state legislation and presidential action the Court held unconstitutional in one 17-month period starting in January, 1935: the NIRA, both its Codes of Fair Competition and the president’s power to control the flow of contraband oil across state lines; the Railroad Retirement Act; the Frazier-Lemke Farm Mortgage Moratorium Act; the effort of the president to get the administrative agencies to reflect his political vision (Humphrey’s Executor); the Home Owners’ Loan Act; a federal tax on liquor dealers; the AAA; efforts of the new SEC’s attempt to subpoena records to enforce the securities laws; the Bituminous Coal Conservation  Act; the Municipal Bankruptcy Act, which Congress passed to enable local governments to use the bankruptcy process; and, perhaps most dramatically, in Morehead v. Tipaldo, minimum-wage laws on the books in a third of the states, in some cases, for decades.  Some of these decisions have withstood the test of time, but most, of course, have not.   . . .

Second, FDR was in as strong a political position as any President has ever been in the modern era.  He had just won 60.8% of the popular vote, the largest popular majority ever at the time.  In the electoral college, he had won 98.5% of the electoral votes (all but the eight votes of ME and VT).  The Court-packing bill was the first piece of legislation FDR put forward after this massive 1936 electoral triumph.  And the 1936 elections were a sweep for the Democrats in the House and Senate, too.  In the Senate, the Democrats held 76 Senate seats, Republicans just 16 (sorry AK and HW, you weren’t states yet).  In the House, Democrats had a 334-88 advantage. . . .

Yet despite FDR’s popularity and the Court’s actions, almost as soon as he announced the Court-packing bill, two-thirds of the newspapers that had endorsed FDR came out vociferously against the plan.  This response was geographically widespread, bipartisan, and intense.  The most common charge was that FDR was seeking “dictatorial powers,” a particularly resonant charge in that era.  . . .

Why was FDR’s decision to engage Court-packing so destructive politically for him and the rest of his domestic agenda?  The simple answer is that, even for the most popular President in modern political history –at the zenith of his popularity — changing the size of the Court for political reasons was widely viewed as a dangerous form of political over-reaching. 
Finally, and perhaps most importantly, when FDR lost the Court-packing fight, he didn’t just lose that one battle:  that battle was politically catastrophic for much of the rest of his domestic political agenda.  Indeed, the fight over Court packing largely killed the progressive legislative agenda until the 1960s.  As FDR’s second vice president, Henry Wallace, observed in looking back at these events: “The whole New Deal really went up in smoke as a result of the Supreme Court fight.”  The next major item on FDR’s agenda had been national health-care; after the Court-packing fight, FDR felt forced to drop the issue.  As a Fortune magazine poll in July 1937 put it: “The Supreme Court struggle had cut into the President’s popularity as no other issue ever had.”  The Republican Party had been declared virtually dead in the wake of the 1936 elections.  But in the 1938 mid-terms, the Democratic Party lost 71 House seats, 6 Senate seats, and 12 governorships; nationwide, the two parties divided the congressional vote almost evenly (all the more remarkable because the Democratic Party had a near monopoly in the South). . . .

But if debates about Court-packing move from campaign rhetoric to potential legislation, it is worth being aware that when the most popular president in history, with a Congress his party controlled overwhelmingly, clashed with the Court that was the most aggressive in American history in pervasively challenging national political power, FDR not only failed to get Court-packing legislation enacted, the effort generated a political firestorm that cost FDR the rest of his domestic agenda.